1. Field of the Invention
The present invention pertains to systems for separating produced gas from crude oil or similar hydrocarbon liquids in a wellbore and whereby the produced gas and oil may be conveyed separately to the surface for further treatment, distribution or reinjection of the gas into nearby wells, for example.
2. Background
In certain wells which produce hydrocarbon liquids, the amount of formation gas entering the well or gas entrained in the liquid entering the well may be significant. Reservoirs which are subjected to pressurized gas injection to stimulate oil flow may produce gas commingled with the oil or gas may migrate to the production wells and flow into the wells at perforations spaced from the perforations which are producing primarily hydrocarbon liquids. If the gas and oil are required to be produced to the surface through the same conduit, elaborate facilities must be provided at the surface for separation of the gas from the oil. The facilities may require substantial reduction of the gas pressure during treatment thereof, thereby requiring costly recompression of the gas for transport or reinjection into a nearby formation.
In certain oil fields such as those of the Alaskan North Slope, the gas/oil ratio from certain wells is particularly high due to natural formation conditions and also due to the use of gas injected into the formation at high pressures to stimulate additional oil flow to producing wells. Accordingly, it has been deemed desirable to reduce the cost of gas/oil separation at the surface resulting from the production of high volumes of gas commingled with the produced oil. Moreover, wells which originally were configured for primarily oil production have not been capable of producing separate streams of downhole separated oil and gas prior to the present invention. Several advantages may be realized from substantial separation of gas from oil in the wellbore and production of the gas and oil through separate conduits to the surface. Surface separation and treatment facilities may be minimal or even eliminated at or near the production well site. If the gas entering the well is at relatively high pressure, the potential energy of this gas may be preserved by producing it to the surface through a separate conduit, thereby reducing the recompression power requirements and, in some instances, the gas may be used for artificial lift or stimulation purposes for nearby wells without requiring any recompression. The present invention has been developed with these desiderata in mind.